Electrically powered air diffusers

ABSTRACT

An air diffuser  10  is provided which comprises a motor  54 , an airflow control element  60  and a transmission between the motor  54  and the airflow control element  60  whereby, when the motor  54  is activated, the control element  60  is displaced either in the direction which allows airflow to increase or in the direction which decreases airflow and wherein the motor  54  is a stepping motor. The motor  54  is mounted on a stationary support structure  22, 26  on a side of the control element  60 , opposite from the supply of air to the diffuser  10.

FIELD OF THE INVENTION

THIS INVENTION relates to electrically powered air diffusers.

BACKGROUND TO THE INVENTION

Two types of air diffuser are widely used for the purpose of controlling the flow of air into a room from a supply duct containing cooled air (in summer) or heated air (in winter).

The first type uses thermally sensitive elements (“pills”) and controls air flow on the basis of the temperature in the vicinity of the diffuser and in the duct.

The second type uses an electric motor, under the control of a temperature sensor, to displace the diffuser's flow control element in movements which restrict or increase the area through which heated or cooled air can flow.

An electronic temperature sensor, which can be at a location remote from the diffuser, senses the temperature in the room. In heating mode, when the room temperature falls below a pre-set lower limit, the motor drives the diffuser's flow control element to a fully open position so that heated air flows in. When the temperature in the room reaches a predetermined maximum, the motor is again actuated to drive the flow control element to a closed position. The closed position is not usually fully closed so that, when the flow control element reaches the end of its travel, some air still flows in.

In cooling mode, when the sensor detects that room temperature is above a predetermined maximum, the motor drives the control element to its fully open position. Cold air flows in from the supply duct. When the room temperature drops to a predetermined level, the motor drives the control element to a fully closed position, or to an almost closed position which allows a volume of cooled air to flow in continuously.

When the air conditioning system is switched on after a period of shut down, say overnight, the motor is driven for a period of time which is more than that required to shift the flow control element to one of its end positions. When the element hits one or other of two end stops provided, the motor continues running. A slipping clutch in the drive system between the motor and the control element permits this to take place. The motor is then driven in the reverse direction against the other end stop. The time period for which the motor is driven is longer than that required for the control element to reach the other end stop. The setup procedure described enables the two end points of the element's travel to be determined. Thereafter, depending on the time for which the motor is driven in either direction, it is possible to position the control element at approximately the desired point in its range of travel.

The motors of air conditioning systems are typically installed in the flow path of air flowing into the room, but this has the disadvantage that they are exposed to hot air during heating (in winter conditions), which could cause overheating and/or reduce motor life. In some diffusers, the motors are attached to the control elements and thus move up and down with them. This has the disadvantages of increased loading of the motor bearings and increased loading the motor during lifting of the control element, both potentially resulting in reduced motor life.

The present invention seeks to provide an improved electrically powered air diffuser in which the control element can be positioned more accurately than is possible with known diffusers. The invention also seeks to provide an improved electrically powered air diffuser in which the motor is substantially protected from the temperatures of the air flowing through the diffuser and wherein the lifting mechanism need not bear the load of the motor.

BRIEF DESCRIPTION OF THE INVENTION

According to the present invention there is provided an air diffuser comprising a casing, a motor, an airflow control element and a transmission between the motor and the airflow control element whereby, the transmission being configured such that, when the motor is activated, rotational movement of the motor is transferred via the transmission to displace the control element relative to the casing either in a direction which allows airflow to increase or in the opposite direction which decreases airflow, wherein the motor is a stepping motor.

The control element may be disposed on a side of the motor from which air is supplied to the diffuser and the transmission may include a threaded shaft that is rotatable by activation of the motor and the control element may be received on the threaded shaft, to be displaced longitudinally along the shaft in screw fashion when it rotates.

The air diffuser may include a stationary support structure that is connected to the casing and the motor may be attached to the support structure.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of non-limiting example, to the accompanying drawings in which:

FIG. 1 is an axial section through an air diffuser in accordance with the present invention;

FIG. 2 illustrates, to a larger scale, the portion of the air diffuser of FIG. 1 which is inside the circle;

FIG. 3 is a pictorial view of an air flow control plate and the parts associated therewith; and

FIG. 4 illustrates, to a larger scale, the part of the structure of FIG. 3 which is within the circle.

DETAILED DESCRIPTION OF THE DRAWINGS

The diffuser 10 shown in the drawings comprises a casing 12 which includes a short sleeve 14 for attachment to the supply duct, a flange 16 which encircles the lower end of the sleeve 14, and a conical section 18 which extends downwardly from the outer edge of the flange 16.

Hangers 20 depend from the flange 16 of the casing 12 and are attached at their lower ends to a stationary support structure in the form of a decorative trim plate 22 (see particularly FIGS. 3 and 4). There is an air flow gap 24 between the edge of the plate 22 and the section 18.

An induction channel 26 (see particularly FIG. 3) extends across the top surface of the plate 22. The channel is closed at the bottom, the top and on each side, but is open at one end 27. The other end of the channel 26 is closed except for two slits 28. A venturi tube 30 extends upwardly from the channel 26 and serves to receive a temperature probe (not shown). The arrangement illustrated promotes air flow over the probe.

The trim plate 22 has a hole 34 at its centre and a perforated cap 36 including a sleeve 38 and an end wall 40 is a push fit in the hole 34. The cap 36, whilst serving to conceal the internal construction, also provides flow paths along which air can flow from the room into the channel 26.

A housing 42 is secured by clips 44 to the channel 26. The housing 42 has a side wall 46 and an end wall 48 the centre portion 50 of which forms a mounting for the power output shaft 52 of a stepping motor diagrammatically shown at 54 in FIG. 2. The drive shaft 52 of the motor connects to a threaded shaft 56 and the motor 54 is secured to the housing 42 by two screws (not shown) passed through holes 58 (FIG. 4) in the housing 42 and into tapped bores of the motor 54.

An airflow control element in the form of an airflow control plate 60 extends across the lower end of the sleeve 14. The periphery of the plate 60 lies, in the closed position as shown in FIG. 1, close to the flange 16 and thus obstructs air flow from the sleeve 12.

There is a dome 62 (FIG. 1) at the centre of the plate 60. A threaded bush 64 is secured to the dome 62 and the shaft 56 is screwed into the bush. When the shaft 56 rotates, the bush travels longitudinally along the shaft 56 so that the flow control plate 60 moves up or down, depending on the direction of rotation of the shaft. As the plate 60 moves down, a gap opens up between it and the flange 16 and air can thus flow from the sleeve 12, through the gap 24 and into the room.

A stepping motor is driven by pulses from an electronic controller. The motor 54 turns a predetermined amount for each applied pulse.

It is thus possible to rotate the motor 54, and hence displace the plate 60, through an accurately determined distance, based on the number of pulses applied. It is also possible to set electronically the end points of the travel of the plate 60.

A further advantage is that feedback from the motor can be used to indicated the exact position of the plate 60. This enables a building automation system (BAS) to make better use of the available air and save energy.

Even if the diffuser is not in a building with BAS, software can be incorporated into the diffuser's controller so that the end points can be accurately predetermined and the set point can readily be adjusted.

It is also possible for a stepping motor to start slowly and then increase in speed, and to slow down as the set point is reached. Should any resistance to movement of the disc 60 be encountered, the motor can be slowed so that its torque increases. Generally, the electronic controller can displace the plate 60 at any desired speed, and at changing speeds, to achieve a desired air flow pattern.

The mounting of the motor 54 on top of the stationary trim plate 22 and induction channel 26 causes it to remain stationary during operation, so that the transmission, including the shaft 56 and bush 64 need not bear the weight of the motor, when activated or when stationary. This means that the weight of the motor 54 is also not borne by the bearings of motor or by any other parts of the motor, so that the life of the motor is not reduced by these loads.

The configuration of the diffuser 10 with the control plate 60 above the motor 54, i.e. on the side of the motor from which air is supplied to the diffuser, causes the motor to be shielded from the supplied air and thus to be protected against temperatures of the supplied air. 

1. An air diffuser comprising a casing, a motor, an airflow control element and a transmission between the motor and the airflow control element whereby, said transmission being configured such that, when the motor is activated, rotational movement of the motor is transferred via the transmission to displace the control element relative to the casing either in a direction which allows airflow to increase or in the opposite direction which decreases airflow, characterised in that said motor is a stepping motor.
 2. An air diffuser as claimed in claim 1, wherein the control element is disposed on a side of the motor from which air is supplied to the diffuser.
 3. An air diffuser as claimed in claim 1, wherein said transmission includes a threaded shaft that is rotatable by activation of the motor and said control element is received on the threaded shaft, to be displaced longitudinally along the shaft in screw fashion when it rotates.
 4. An air diffuser as claimed in claim 2, wherein said transmission includes a threaded shaft that is rotatable by activation of the motor and said control element is received on the threaded shaft, to be displaced longitudinally along the shaft in screw fashion when it rotates.
 5. An air diffuser as claimed in claim 2, which includes a stationary support structure that is connected to the casing and wherein said motor is attached to the support structure.
 6. An air diffuser as claimed in claim 4, which includes a stationary support structure that is connected to the casing and wherein said motor is attached to the support structure. 